The present invention relates generally to devices for use in orally dispensing medication using an inhaler. More specifically, the present invention relates to spacers used for facilitating the delivery to pediatric and breathing impaired patients of medication dispensed from an inhaler.
Medications are commonly dispensed from pressurized metered dose inhalers (MDI) to deliver the medication directly to the lungs of a patient. Spacers are used for transporting the medication from the spray outlet of the MDI to the patient's mouth. The spacer is intended to increase the effectiveness of drug delivery to the deep lung regions of the patient primarily by decelerating the drug spray before the spray enters the patient's mouth. The spacer will also reduce the size of spray droplets (by evaporation) and trap larger particles in the spacer. This will reduce the need for hand-breath coordination and allow for multiple breath inhalation therapy, thereby improving the overall delivery of the medication dose to the lung. These factors are particularly important when trying to effectively provide inhalation therapy to children and to patients with breathing impairments.
The quantity, size, and velocity of the drug particles that exit an inhalation spacer are affected by dynamic interactions between the spacer, spray properties, and airflow. Unfortunately, in conventional spacers, as much as 50% of the medication is lost before delivery to the patient because of inefficient design of the spacer itself. For example, high-pressure, recirculation zones are created near sharp corners in the spacer. These recirculation zones trap spray particles and provide increased time for particle deposition on the spacer walls such that they are not delivered to the patient. Also, while it is known that medication particles having a diameter in the range of 3–5 microns are desirable for delivery to deep lung tissue, conventional spacers do a poor job of consistently delivering particles of this size. This is because existing spacer designs do not effectively control the heat exchange rate and the length of time that the medication particles remain inside the spacer, factors which directly affect particle size. Finally, prior art spacers typically include air inlets at the upstream (spray discharge) end near the mouthpiece but they cannot maintain consistent flow energy. All of these factors will cause undesirable deposition of the medication droplets in the oro-pharyngeal region of the patient. The inefficient delivery of medication to the deep lung results in either under-medication of the patient or the waste of expensive medications.
U.S. Pat. No. 6,367,471 discloses an internal vortex mechanism for an inhaler device. More specifically, vortex generators positioned within the wall of the conduit and in fluid communication with air inlets for receiving ambient outside air, provide the inner wall of the conduit with a circumferential-swirling turbulent boundary layer flow to minimize impaction of the medication on the inner surfaces of the conduit. The inhaler device shown in FIG. 1 of the patent contains only one chamber. The apparatus also includes a medication dispenser supported in the housing and adapted to dispense a dose of aerosolized medication into the conduit, a plurality of air inlets positioned on the outer surface of the conduit and a plurality of vortex generators positioned within the wall of the conduit downstream of the medication dispenser. Each vortex generator includes a first generally pyramid-like portion having an apex and an open base forming an outlet located on the inner surface of a second generally pyramid-like portion having an apex and an open base in fluid communication with a corresponding air inlet.
U.S. Patent Application Publication 2002/0121275 discloses an aerosol enhancement device. More specifically, the aerosol enhancement device displayed in FIGS. 1–6 provides a single chamber. The air inlet port is positioned centrally with respect to the spacer.
U.S. Pat. No. 6,234,169 discloses an inhaler. The inhaler provides a conduit defining an air flow path extending between the first end and the second end and an orifice in the chamber between the first end and the second end, the orifice utilizing the Coanda Effect when the reservoir is in air flow communication with the chamber and upon inhalation by the individual to draw medication from the reservoir. As seen in FIGS. 1–6, the inhaler has only a single chamber with the positions of air inlet shown in the Figures.
What is needed, then, is a spacer and method of use thereof for the efficient delivery of medication from a metered dose inhaler, through the spacer, and into the patient. Such a spacer would be easy to use and substantially improve the delivery of medication to the patient's lungs.